Process for aromatizing olefins in the presence of easily cracked paraffins

ABSTRACT

PROCESS FOR AROMATIZING A FEEDSTOCK, WHICH MAY BE LIQUID OR GASEOUS AND IS HYDROCARBON IN NATURE HAVING A BOILING RANGE OF ABOUT C2 TO 400*F. BY CONTACTING THE FEEDSTOCK WITH A ZSM-5 TYPE OF CATALYST UNDER AROMATIZATION CONDITIONS WHEREBY MAKING A MIXED GAS AND LIQUID PRODUCT, SEPARATING THE GAS AND LIQUID FRACTIONS OF THE   PRODUCT, SUBJECTING THE GAS FRACTION OT DEHYDROGENATIVE CRACKING TO INCREASE THE PROPORTION OF OLEFINS AND LIGHT GASES THEREIN, SEPARATING AND RECYCLING THE OLEFIN RICH PORTION TO ADMIXTURE WITH THE ORIGINAL FEEDSTOCK, AND RECOVERING LIQUID GASOLINE OF VERY HIGH OCTANE.

May 28, 1974 E. N; GIVENS ETAL 3,813,330

PROCESS FOR AROMATIZING OLEFINS IN THE PRESENCE OF EASILY CRACKEDPARAFFINS Filed March 5. 1975 2 Sheets-Sheet 1 REACTOR May 28, 1974GWENS ETAL 3,813,330

PROCESS FOR AROMA'llZlNG OLEFINS 1N THE PRESENCE I OF EASILY CRACKEDPARAFFTNS FIGZ REACTOR 2?. Sheets-Sheet 2;

p 3,813,330 Patented May 28, 1974 y difiraction TABLE 1 Interplanarspacing d(A): Relative intensity tinguishing crystalline structure whoseX-ra pattern shows the following significant lines:

, Woodbury,

. 3813330 PROCESS FOR ARoMATrzrNG OLEFINS IN THE PRESENCE OF EASILYCRACKED PARAFFINS United States Patent O "ice WWWWWWWWWW MWWW n u n u u8755322 22 .nnnn 0111000000000000 +2 1O+ 476l05514494 LQAJBDSJD WQ NJWDSB 11776655544333322 w M w m m a a mwmmw s m fi W fiwefi r l v m mi ad o C vn o n H m im e a g 7 flo s e n E h mm m o m 1 mrs m 7 mwm oeaflme J" v S w m mfie vmk 7 0 B m e 3 u e N 3 L do. m Of Wef .0 C 1 t 0.111d o S nFWm r. H I &0 a ny cm 7 D b a mocd e t L3 err m tune-1 P e 630 cr e g E C4 3 0 S n f D h m wm em C p Sr-a .m M F mewnwwmwewepgm n C Y ei 0 .Ei Lo m. W mm wt T m wmm mm w m C m sm g m M m Z n wPt md m mdu anc m mmkm ,m r S os nd 31m 8 g m Pb .1 w.. 0.. gm mewmm d 2 A m d em C .0d m .M C H m S 0 r- 11 mm s Pmn nmm a 0 0 W 0 I r. a O at U HbffiPPc Pttataaaaaaaaaaaa R8013 AgNO;

y data were deadiation was the ompositions. Ion s reveals substan-'iikikiomamamanaamaomaemaflaomi ment.

CaClg the Bragg angle, were read these the relative in- MS=mediumstrong, =very strong. It should be.

ction pattern is char- 1 77915252509562 .459 %WH%MH%%MOHW%32008877664433.10

. 7 7 GHQflinmnmiii iikdzz amamomqmamqmamamomnmam ques. The r ip chart.pen recorder was used. and the positions as a function of theinterplanar spacing in A, ded lines, were calculated. In ities are givenin terms of the strong, M-=medium,

r, depending on the silicon to urmnum ratio of the particular sample, aswell as if H01 NaCl These values, as well as all other X-ra termined bystandard techni K-alpha doublet of copper, and a scintillation counterspectrometer with a str The peak heights, I 2 times theta, where thetais from the spectrometer chart. From tensities, 100 I/I where I is theintensity of the strongest line or peak and d(obs.) corresponding to therecor Table 1 the relative intens' symbols S 5 MW=medium weak and VSunderstood that this X-ray difira acteristic of all the species of ZSM-5c exchange of the sodium ion with cation tially the same pattern withsome minor shifts ininter- 40 planar spacing and variation in relativeintensity. Other minor variations can occu al it has been subjected tothermal treat As made covering liquid gasoline of very high octane.

This invention relates to the production of very high 25 octanegasoline. It more particularly refers to the aromatization of analiphatic feed in exceptionally high yields.

There has recently been developed new technology on the aromatization ofaliphatics. This technology is based on the use of a particular class ofsynthetic alumino silicate zeolite molecular sieves of the ZSM-S typewhich may or may not have additional or alternative metal and/ or othercationic components therein. The catalyst used for this known processhas been stated to be a ZSM-S type of catalyst which includes ZSM-5,ZSM-8, and ZSM-ll and other similarly behaving zeolites.

ZSM-S is disclosed and claimed in copending application Ser. No.865,472, filed Oct. 10, 1969, now US. Pat. 3,702,886; ZSM-8 is disclosedand claimed in copending application Ser. No. 865,418, filed Oct. 10,1969, now abandoned and ZSM-ll is disclosed and claimed in copendingapplication Ser. No. 31,421, filed Apr. 23, 1970, now US. Pat.-3,709,979.

The family of ZSM-5 compositions has the characteristic X-raydiffraction pattern set forth in Table 1 hereinbelow. ZSM-S compositionscan also be identified terms of mole ratios of oxides, as follows:

0.9:l20.2 M20: W203: b YO Z H2O wherein M is a cation, n is the valenceof said cation, W is selected from the group consisting of aluminum andgallium, Y is selected from the groupconsisting of silicon andgermanium, z is from 0 to 40 and b is at least 5 and preferably 15-300.

In a preferred synthesized form, the zeolite has a formula, in terms ofmole ratios of oxides, as follows:

0.9i0.2 M 0: A1 0 15-100 SiO t z H 0 and M is selected from 'thegroupconsisting of amixture of alkali metal cations, especially sodium, andalkylammonium cations, the alkyl groups of which preferably contain 2-5carbon atoms. a In a preferred embodiment of ZSM-5, W is aluminum, Y issilicon and the silica/alumina mole ratio is at least 15, preferably atleast 30-.

Members-of the family of ZSM-5 zeolites which include ZSM-S, ZSM-S andZSM-ll possess a definite dis- TABLE--Continned As made H01 N 2301 CaClzReCls AgN a 2. 45 2. 42 2. 42 2. 42 2. 4O 2. 39 2. 40 2. 40 2. 40 2. 392. 40 2. 40 2.38 2.35 2. 38 2. 33 2. 33 2. 32 2. 33 2. 30 2. 24 2. 23 2.23 2. 20 2. 21 2. 20 2. 18 2. 18 2. 17 2. 17 2. 13 2. 13 2. 11 2. 11 2.10 2.08 2.08 2. 07 2. 07 2. 04 2.01 2. 01 2. 01 2. 01 2. 01 1.99 2.00 1. 99 1. 99 1. 99 1. 97 1. 96 1. 95 1. 95 l. 95 a 1. 94 1 92 1 92 1.92 1. 91 1. 88 1. 87 1. 87 1. 87

Partieularly Broad Preferred preferred OH-ISlOz. 007-10 0. 1-0.8 0. 2-0.75 0. 2-0. 95 0.3-0.9 0.4-0.9

OIOH 10-300 10-300 10-300 YO WzO; 5-100 -60 10-40 wherein R is propyl, Wis aluminum and Y is silicon. This mixture is maintained at reactionconditions until the crystals of the zeolite are formed. Thereafter thecrystals are separated from the liquid and recovered. Typical reactionconditions consist of a temperature of from about 75 C. to 175 C. for aperiod of about six hours to 60 days. A more preferred temperature rangeis from about 90 to 150' C., with the amount of time at a temperature insuch range being from about 12 hours to days.

The digestion of the gel particles is carried out until crystals form.The solid product is separated from the reaction medium, as by coolingthe whole to room temperature, filtering and water washing.

ZSM-S is preferably formed as an aluminosilicate. The composition can beprepared utilizing materials which supply the elements of theappropriate oxide. Such compositions include, for an aluminosilicate,sodium aluminate, alumina, sodium silicate, silica hydrosol, silica gel,silieic acid, sodium hydroxide and tetrapropylammonium hydroxide. Itwillbe understood that each oxide component utilized in the reaction mixturefor preparing a member of the ZSM-S family can be supplied by one ormore initial reactants and they can be mixed toegther in any order. Forexample, sodium oxide can be supplied by an aqueous solution of sodiumhydroxide, or 'by an aqueous solution of sodium silicate;tetrapropylammonium cation can be supplied by the bromide-salt. Thereaction mixture can be prepared either batchwise or continuously.Crystal size and crystallization time of the ZSM-S composition will varywith the nature of the reaction mixture employed.

ZSM-8 can also be identified, in of oxides, as follows:

terms of 'mole ratios wherein M is at least one cation, n is the valencethereof and z is from 0 to 40. In a preferred synthesized form, thezeolite has a formula, in terms of mole ratios of oxides, as follows:

0.92120-2 M 0: A1203: S103: Z H20 and M is selected from the groupconsisting of a mixture of alkali metal cations, especially sodium, andalkylammonium cations, especially tetraethylammonium cations.

Zeolite ZSM-8 can be suitably prepared by reacting a water solutioncontaining either tetraethylammonium hydroxide or tetraethylammoniumbromide together with the elements of sodium oxide, aluminum oxide, andan oxide of silica.

The operable relative proportions of the various ingredients have notbeen fully determined and it is to be immediately understood that notany and all proportions, of reactants will operate to produce thedesired zeolite. In fact, completely different zeolites can be preparedutilizing the same starting materials depending upon their relativeconcentration and reaction conditions as is set forth in U.S. 3,308,069.In general, however, it has been found that when tetraethylammoniumhydroxide is employed, ZSM-S can be prepared from said hydroxide, sodiumoxide, aluminum oxide, silica and water by reacting said materials insuch proportions that the forming solution has a composition in terms ofmole ratios of oxides falling within the following ranges:

SiO /Al O from about 10 to about 200 Na o/tetraethylammoniumhydroxide-from Tetraethylammonium hydroxide/Si0 from about 0.08

H oftetraethylammonium hydroxide-from about to about 200 O.9i0.3 M 0} A10 20-90 S10 2 H 0 about 0.05

wherein M is at least one cation, n is the valence thereof and z is from6 to 12. In a preferred synthesized form, the zeolite has a formula, interms of mole ratios of oxides, as follows:

0.9103 M O:Al O :20-'90 SiO-gzz H 0 and M is selected from the groupconsisting of a mixture of alkali metal cations, especially sodium, andtetrabutylammonium cations.

wherein R X is a cation of a quaternary compound of an element of GroupV-A of the Periodic Table, W is aluminum or gallium and Y is silicon orgermanium maintaining the mixture until crystals of the zeolite areformed. Preferably, crystallization is performed under pressure in anautoclave or static bomb reactor. The temperature ranges from 100-200 C.generally, but at lower temperatures, e.g. about 100 C., crystallizationtime is longer. Thereafter the crystals are separated from the liquidand recovered. The new zeolite is preferably formed in analuminosilicate form.

An embodiment of this catalyst resides in the use of a porous matrixtogether with the ZSM-S type family of zeolite previously described. Thezeolite can be combined, dispersed, or otherwise intimately admixed withthe porous matrix in such proportions that resulting products containfrom 1 to 95% by weight and preferably from to 70% by weight of thezeolite in the final composite.

The term porous matrix includes inorganic compositions with which thezeolites can be combined, dispersed or otherwise intimately admixedwherein the matrix may be catalytically active or inactive. It is to beunderstood that the porosity of the composition employed as a matrix canbe either inherent in the particular material or it can be introduced bymechanical or chemical means. Representative of matrices which can beemployed include metals and alloys thereof, sintered metals, andsintered glass, asbestos, silicon carbide, aggregates, pumice,firebrick, diatomaceous earths, alumina and inorganic oxides. Inorganicoxide compositions, especially those comprising alumina and those of asiliceous nature are preferred. Of these matrices inorganic oxides suchas clay, chemically treated clays, silica, silica alumina, etc. as wellas alumina, are particulrly preferred because of their superiorporosity, attrition resistance and stability.

Techniques for incorporating the ZSM-S type family of zeolites into amatrix are conventional in the art and are set forth in US. 3,140,253.

It is to be noted that when a ZSM-S type zeolite is used in combinationwith a porous matrix, space velocities which may be set forth asparameters for this process are based on the ZSM-S type zeolite aloneand the porous matrix is ignored. Thus, whether a ZSM-S type zeolite isused alone or in a porous matrix, the space velocities in all casesrefer to the ZSM-S type component.

It is known that zeolites, particularly synthetic zeolites can havetheir composition modified by impregnating certain metals thereontoand/or thereinto. The composition can also be modified by exchangingvarious anions and/ or cations into the crystal structure of thezeolite, replacing more or less of the ions originally present uponproduction of the zeolite.

The ZSM-5 type family of zeolites have been found to be especiallyactive for aromatization if they have at least a portion of the originalcations associated therewith replaced by any of a wide variety of othercations according to techniques well known in the art. Typical replacingcat-.

ions would include hydrogen, ammonium, and metal cations, includingmixtures of the same. Of the replacing cations, preference is given tocations of hydrogen, ammonium, rare earth, magnesium, zinc, calcium,nickel, and mixtures thereof. Particularly effective members of theZSM-5 type family of zeolites are those which have been based exchangedwith hydrogen ions, ammonium ions, zinc ions or mixtures thereof. Mostespecially zinc ZSM-5 is the best presently known catalyst foraromatizations as set forth.

Typical ion exchange techniques would be to contact a ZSM-S type ofzeolite with a salt of the desired replacing cation or cations. Althougha wide variety of salts can be employed, particular preference is givento chlorides, nitrates and sulfates.

Representative ion exchange techniques are disclosed in a wide varietyof patents, including US. 3,140,249; 3,140,251; and 3,140,253.

It is also within the scope of the aromatization process to which thisapplication is directed to incorporate a desired metallic component ontothe ZSM-S type family of zeolites by techniques other than ion exchange.Thus, for example, it is possible to impregnate a desired metalliccomponent, such as zinc, platinum or palladium, thereinto byconventional impregnation techniques, as well as merely depositing theelemental metal onto the particular zeolite and in some cases, such aswith zinc oxide, to incorporate the metal by physical admixture of thezeolite with an insoluble metal compound.

In any event, following contact with a salt solution of the desiredreplacing cation, the zeolites are preferably washed with water anddried at a temperature ranging from 150 to about 600 F. and thereafterheated in air or inert gas at temperatures ranging from about 500 F. to1500 F. for periods of time ranging from 1 to 48 hours or more. It isnoted that this heat treatment can be carried out in situ, i.e. whilethe particular aromatization reaction is taking place, but it ispreferred to carry it out as a separate step prior to carrying out thearomatization reaction.

This new aromatization technology is also based on carefully definingprocess conditions so as to maximize the conversion of aliphatics toaromatics at reasonably high yields. The important basic processparameters are set forth in applications Ser. No. 153,855, now Pat. No.3,760,- 024 and Ser. No. 253,942, now Pat. No. 3,756,942, filedrespectively on June 16, 1971 and May 17, 1972.

According to these applications the process is carried out atsubstantially any desired pressure, at a space velocity of up to about15 WHSV, at a temperature of about 650 to 1500 F., at a conversion of atleast about and under such combination of conditions as to assure anaromatics yield of at least 30 weight percent based on the aromatizableportion of the feedstock.

In operating this aromatization process, it has been found thataromatics pass through the system substantially unchanged and that thisis a cyclical process in that the catalyst must be regenerated from timeto time. It has also been found that, in addition to the fine liquidyields It is therefore an object of this invention to provide a modifiedaromatization of aliphatics process.

It is another object of this invention to provide an aromatizationprocess having an improved aromatics yield.

It is a further object of this invention to provide a modifiedaromatization process having a decreased propane yield.

Other and additional objects of this invention will become apparent froma consideration of this entire specification including the claims anddrawing hereof.

Understanding of this invention will be facilitated by reference to theaccompanying drawing in which:

FIG. 1 is a schematic fiow diagram of one form of the process of thisinvention; and

FIG. 2 is a schematic flow diagram of a modified form of the processshown in FIG. 1.

In accord with and fulfilling these objects, one aspect of thisinvention resides in a process comprising charging a feedstockcomprising aliphatic hydrocarbons having a boiling point of C to 400 Fto a reaction zone maintained at about 650 to 1500 F. and at a pressureof about to 35 atmospheres; contacting such feedstock in the absence ofadded hydrogen with a ZSM-S type of catalyst in said reaction zone at aspace velocity equivalent to a fixed bed space velocity of about 1 to 15WI-ISV to form a mixed gas and liquid product, which gas compriseshydrogen and low molecular weight paraffins and which liquid comprisesaromatic hydrocarbons; separating said gas from said liquid; recoveringat least the aromatics portion of said liquid product; subjecting thegas product to dehydrogenative cracking conditions to produce a mixtureof a gas comprising hydrogen and methane and a fraction comprisingolefins; and recycling said olefins fraction into admixture with saidfeedstock. According to one aspect of this invention the liquid productcomprising aromatics can be used as such as a high octane gasoline blendstock. According to another aspect of this invention the liquid productcan be treated so as to remove light ends there from which light endscan be fed to the dehydrogenation cracker or to the gas byproductstream. If desired, heavy ends can be taken from the liquid aromaticsproduct in a distillation or other procedure. As a further alternative,thearomatics product can be resolved into its component compounds, e.g.benzene, toluene, xylene, naphthalene, etc., and these used or sold forchemical use.

The catalyst in the reactor can be in the form of pellets or particlesof any convenient size and consistency. The catalyst may be in a fixedor fluidized bed with the feedstock passing upwardly (gas or liquidfeed) or down wardly (liquid feed) therethrough. The feedstock can passover a catalyst bed which may or may not be vibrated. However, this isthe-least desirable of these three alternatives.

In one other aspect of this invention, the ZSM-S type catalyst isintentionally predeactivated with respect to part of the feed. In thisaspect of this invention the ZSM-S catalyst is pretreated so as torender it substantially inert with respect to low molecular weightparafiins such as propane and ethane. This can be accomplished bysteaming the catalyst for about 20 hours with saturated steam at about122S F. It can also be accomplished by utilizing the catalyst toaromatize propane, for an appropriate time at an appropriatetemperature, regenerating the catalyst, reusing such, and continuingthis cycle until the effectiveness of the catalyst for propanearomatization has diminished sufliciently. This aromatization processcan then operate under relatively milder conditions sufiicient toaromatize the olefin, naphthene and longer chain paraffin portions ofthe feedstock, with the lower molecular weight parafiins passing throughthe aromatization reaction zone substantially unconverted. The parafiinsthat pass through the aromatization reaction zone become part of the gasproduct which is then dehydrogenated in a cracking unit.

Paraffin cracking and dehydrogenation to olefins is per so well known inthe chemical and petroleum arts. Many plants are in operation around theworld for making ethylene and/or propylene plus more or less otherolefins such as butene from various feedstocks such as naphtha, propane,butane, mixed ethane and propane, and even methane. These plants areoperated utilizing either thermal or catalytic cracking. The mostdifficult, and therefore the most expensive, part of an olefins crackeris the resolution of the product into ethylene, propylene and otherindividual compounds of suificient purity to be used in further chemicalprocessing, particularly polymerization.

According to the art, a feed stream of saturated hydrocarbons,preferably mainly propane or a propane-ethane mixture, is passed, in thegas phase, through a bed of solid catalyst particles. The catalyst maybe a Group VI oxide or the like with or without supporting alumina, clayor the like. In the alternative, the parafiinic feed may be passedthrough a tube furnace at a temperature high enough to sustain thermalcracking, e.g., about 1400 to 2200 F. at 5 to 50 p.s.i.a. With anethane-propane feedstock, these paraflins may be fed together orseparately to a pyrolysis (cracking) furnace. It has been proposed toincorporate in the feed one or more materials which react readily withhydrogen so as to promote the dehydrogenation of the paratfins. Thesematerials include sulfur, sulfurdioxide, nitrogen oxides, etc. Thethermal pyrolysis tubes are preferably stainless steel. The crackingcatalyst, where used, is preferably chromium oxide, nickel oxide ortitanium dioxide on an alumina or ceramic base. The catalytic processoperates at about 900 to 1400 F. at slightly elevated pressures of about1 atmosphere. The catalyst is regenerated in air at about 1100 to 1300F.

In conventional processing, the gaseous product of a thermal orcatalytic dehydrogenation and cracking process is subjected to a verysophisticated work-up and purification technique. The gas product isquenched, compressed, dried and then subjected to a multipledistillation system usually involving at least four (4) and sometimeseven six (6) columns. In some product recovery schemes there are alsoabsorption and extraction unit operations. Since sulfur is often used asa hydrogen scavenger, acidic corrosive conditions exist in thepurification train requiring the use of large amounts of corrosionresistant equipment.

In contrast to this known state of the art, in the process of theinstant invention the olefins product need not be purified to any extentgreater than separation of permanent gases, such as hydrogen andmethane. The rest of the pyrolysis product is simply recycled toextinction. Since a simple separation of (22+ and C is all that isrequired for the instant process, this can be accomplished by partialcondensation at a temperature which will assurethat the final gasproduct stream contains substantially nothing boiling higher thanmethane. It is of course unlikely that a pure gas stream of C, will beproduced. However, this is not of dire consequence since this gas streamis principally used for its heat value rather than further chemicalprocessing.

It is also a remarkable attribute of this process that sul for values donot seem to adversely effect the ZSM-S type of aromatization catalystand therefore sulfur values, used to scavenge hydrogen and drive thepyrolysis reaction, can be recycled through the aromatization reactionzone, if desired, with substantial impunity. Consideration of therelative boiling points of methane, hydrogen sulfide andieth yleneindicates that partial condensation of the pyrolysis,

product sufficient to take out ethylene, propylene and other olefinsshould also take out hydrogen sulfide. Thus the gas product from thispartial condensation should bev substantially sulfur free or at leastshould have relatively to FIG. 1 thereof. A feed stream 10, which issuitably a mixture of paraflins, olefins and naphthenes which may havesome aromatics admixed therewith, is fed into a re-.

actor 12 at least partially filled with catalyst 14. Suitable heat inputmeans (notshown) is provided to maintain the temperature in the reactorat the desired level to convert substantially all of the olefinic andnaphthenic portion of the feed stream, and-perhaps some of theparaffinic portion of the feed stream to aromatics and to light gases16. This mixed product 16 passes through a line 18 into a suitableseparator 20 by which the, aromatics are recovered as a liquid phase 22and the lighter products are recovered as a gas phase 24. Theilight'gasphase products are fed through a line 28 to a pyrolysis unit 26 in whichthe light gases, composed mainly of paraffins in the C to C range, arepyrolyzed to abstract hydrogen and crack the parafiins into olefins ofgenerally average shorter carbon chain length than the parafiin feed.The product 30 from the pyrolysis is resolved 32 into a gas productstream 34 and a recycle olefin rich stream 36. This latter stream 36 iscombined with the original fresh feed 10 to make the full feed 38 to thereactor.

The liquid product recovered from the separator 20 passes through aconduit 40 into a flasher or partial condenser 42 where any retainedresidual gases are vaporized and passed through a conduit 44 intoadmixture with the gas 34 from the olefin recovery column 32 to form aproduct gas stream 46. The rafiinate 48 from the flasher or partialcondenser 42 is highly aromatic, high octane gasoline blend stock.

The modification of the process of this invention shown in FIG. 2utilizes a fresh feed 10 similar to that used in the process of FIG. 1.The aromatization reactor 12 and catalyst 14 therein are similar tothose shown in FIG. 1 as are the gas/liquid product takeolf andresolution to form a gas product 28 and a liquid product 40. In thisembodiment of this invention, the processing of the liquid productstream 40 is somewhat difierent in that it is fed to a first column 50in which residual gases 52, such as methane and hydrogen, are strippedoff and combined with the C gas 34 from the olefin column 32 to form thegaseous product 54. The rafimate 56 from the first column 50 containssubstantially all of the aromatics and any C -laliphatics which werepresent in the liquid product of aromatization. This raffinate 56 isthen subjected to resolution in an aromatics column to separate thearomatics 58 from the aliphatics 60. This separation may be byfractional distillation, fractional crystallization, solvent extractionor otherwise (not particularly shown) as is in the prior art. Thealiphatics stream 60 is substantially saturated and is combined with thegas product stream 28 from aromatization as a mixed feed 62 to thecracker 26.

The liquid product resulting from this process is a mixture of benzene,toluene, xylenes and ethyl benzenes with lesser amounts of otherpolyalkyl benzenes and some fused ring aromatics such as naphthalene andvarious alkyl naphthalenes. The gas product resulting from this processis predominantly methane and hydrogen with lesser amounts of carbonoxides and higher paraffins. Other minor impurities may exist in eitherthe liquid or the gas product stream.

This invention will be illustrated by the following examples which arenon-limiting on the scope of this invention and in which parts andpercentages are by weight unless expressly stated to the contrary.

EXAMPLE 1 Ethylene 13 Ethane 15 Propylene 6 Propane 16 EXAMPLE 2'Product gas from Example 1 is fed to a thermal pyrolysis unit operatingat 15001650 F. A product stream as shown in Table 3 containing about 42%C -C olefins is evolved. The olefin portion of this pyrolysis product isrecycled as aforesaid while the C gas fraction is combined with gasevolved from the aromatics rich liquid product to form amethane/hydrogen rich product gas at a rate of 63 parts per hour.

TABLE 3 Aromatiz prod. Pyrolysis Charge total product Recycle What isclaimed is:

1. A process comprising:

(A) feeding a composition comprising at least one member selected fromthe group consisting of olefins, naphthenes and long chain parafiins toan aromatization zone containing a ZSM-5 type of catalyst at a spacevelocity equivalent to about 1 to 15 WHSV and a temperature of about 650to 11400 F.;

(B) maintaining said composition in said aromatization zone for a timeand under conditions suflicient to convert at least 90% of saidcomposition to a product containing at least a 30 weight percent yieldof liquid form aromatics and a gas;

(C) resolving said aromatization product into a liquid phase product anda gas phase product wherein said gas phase product is preponderantlyparaffins and said liquid phase product is preponderantly aromatics;

(-D) pyrolyzing and dehydrogenating said gas phase product to produce amixture comprising olefins and 1- (E) recycling said olefins from step Dinto admixture with said feed composition to said aromatization; and

(F) recovering a liquid, high octane, substantially aromatic product anda gaseous, substantially methane and hydrogen, product.

2. A process as claimed in claim 1 wherein said feed compositionadditionally contains paraflins and aromatics.

3. A process as claimed in claim 1 wherein said aromatization catalystis Zn ZSM-S.

4. A process as claimed in claim 1 wherein the liquid phase product ofaromatization is resolved to remove 11 12 substantially all residual gastherefrom which residual References Cited I gas is admixed with said gasproduct. UNITED STATES PATENTS 1 5. A process as claimed in claim 1wherein said ali- 3 542 667 11/1970 McMahon et al. 208 66 phaticcomponents are resolved to provide a C fraction 'f which is fed to SaidStep D. 5 3,556,987 1/1971 zimmerman et a1. 208- 66 6. A process asclaimed in claim 1 wherein said pyro- HERBERT LEVINE, Primary lyzing iscatalytic.

7. A process as claimed in claim 1 wherein said pyro- US, Cl, X R lyzingis thermal. 48-497 R, 211

mg? UNTTED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,813,330 Dated M vQB. lqjli Inventor) EDWIN N. GIVENS, CHARLES J. PLANKand EDWARD J. ROSINS K It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown' below:

Colum'n 2, line ML before table insert Table II X-Ray Diffraction ZSM-5Powder in Cation Exchanged Forms d spacings Observed Column 3, line 13omit, line repeated.

Signed and sealed this 12th day of November 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. I C. MARSHALL DANN Attesting Officer Commissioner ofPatents

